Members of staff from the UK embassy in the capital Addis Ababa are among those missing in the north of the country, close to the Eritrean border.

A further seven French nationals and up to 13 Ethiopians are also believed to have gone missing on a trip to look at geological sites.

The group disappeared last Sunday while travelling in the inhospitable east of the country, 500 miles north of Addis Ababa.

Bandits and rebel groups operate in the isolated area and visitors travel with armed guards as well as local guides.

It was reported today that a special forces rescue team is on standby to try to free the captured party.

Mekele, the largest town in the area, is believed to be the staging post for diplomats and other rescuers.

The Prime Minister is being kept aware of developments and Foreign Secretary Margaret Beckett said the Government was doing all it could to resolve the situation.

Mrs Beckett said the missing Britons include members of staff from the British Embassy, or relatives of members of staff.

Rossanna Moore, wife of Michael Moore, the director of the British Council in Ethiopia, is thought to be among those missing.

The group is thought to have been in a convoy of four vehicles in Dalol, in the Afar region of the country, travelling to see the salt mines.

Dalol is one of the lowest and hottest places on earth, with an average annual temperature of 35C (95F).

One man, who has led 10 expeditions to Ethiopia, said bandits are a common hazard in the region.

Col John Nicholas Blashford-Snell, 70, who has been kidnapped twice in the same desolate region, said they are motivated by desperate poverty, not politics.

Mrs Beckett said: "We have already been working very closely with Ethiopian authorities, through our Ambassador in Addis Ababa.

"In London, Lord Triesman, Minister for Africa, spoke to the Ethiopian Ambassador. They have made it clear that they are doing all they can to ensure that the situation is resolved peacefully. We are also co-ordinating with other governments."

She added: "At this time our thoughts are very much with the family members of our staff and the other nationals in what will be a very difficult and traumatic time."

In the wake of the crisis, the Foreign Office recommended that people do not travel to the Afar and Danakil regions.